Dynamic-DNS client in the device via GnuDIP

As an alternative to using a simple HTTP request to update DynDNS information, some services make use of the GnuDIP protocol. The GnuDIP protocol is based on a challenge-response mechanism:

  1. The client opens the connection to the GnuDIP server.
  2. The server responds with a random value calculated for the session.
  3. The client uses the random value and the password to create a hash value, which is returned to the server.
  4. The server checks this hash value and reports its result by sending a number back to the client.

The GnuDIP protocol can exchange the messages between the client and server either via a simple TCP connection (standard port 3495) or as a CGI script running on an Internet server. The version using an HTTP request from a CGI script has the advantage that no additional ports have to be opened on the GnuDIP, and also that HTTP offers protection from passive interception and offline dictionary attacks.

Requests to a GnuDIP server are triggered by the device with an action in the following form:

In response to the request, the GnuDIP server returns one of the following values to the GnuDIP client (assuming that the connection between server and client was established):

These responses can be processed by the device's actions to trigger further actions if necessary.

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